Process for the purification of industrial effluents

ABSTRACT

A novel process for purifying industrial effluents which comprises bringing said effluents into contact with cellulosic absorbent which has been pretreated with precipitants.

This is a divisional of application Ser. No. 575,279, filed on May 7,1975, now U.S. Pat. No. 4,025,428; which is a division of applicationSer. No. 356,853, filed May 3, 1973, now abandoned.

The present invention relates to a process for the purification ofindustrial effluents, especially for the decolourisation of wasteliquors arising in the textile, paper and leather industry, which ischaracterised in that the effluents are brought into contact withcellulosic absorbent which has been pretreated with precipitants.Preferably, filters of cellulose itself or of waste sheets from printingare used.

The purification of industrial effluents is a problem and provesextremely difficult particularly when the removal of water-solubleorganic substances is concerned.

As part of this problem, the decolourisation and purification ofeffluents arising in the textile, paper and leather industry is anurgent requirement.

Various proposals have already been made for removing residues ofdyestuffs and auxiliaries from industrial effluents. Thus, for example,it has been provided that the residual liquors, including wash waters,are collected in collecting tanks and that the residues of dyestuffs andauxiliaries are precipitated therein by addition of suitableflocculating agents and separated out by sedimentation and filtration.However, these processes suffer from various disadvantages. Above all,the volumes of water to be treated are extremely large and sedimentationis frequently protracted.

Surprisingly, it has now been found that a complete or at least veryextensive purification, including decolourisation, of industrialeffluents is achieved if these are brought into contact with absorbentswhich consist of cellulose pretreated with precipitants. The processaccording to the invention is above all suitable for the removal ofanionic dyestuffs, optical brighteners, dyeing auxiliaries and washingagents, and for the elimination of residues of tanning agent.

By means of the process according to the invention it is not onlypossible extensively to free incompletely spent treatment liquors fromthe abovementioned substances but also satisfactorily to purify thecorresponding liquors which have been diluted with rinsing effluents andwhich in most cases contain mixtures of dyestuffs and washing agents.

Because of its broad applicability, the present process permits a savingof fresh water, through possible recirculation of residual liquors orwaste liquors which arise, such saving being demanded with everincreasing urgency at the present time.

Where residual liquors or waste liquors are spoken of in the processaccording to the invention, the effluents of the textile, paper andleather industry which arise in connection with dyeing, washing andtanning processes are above all concerned, regardless of the apparatusemployed. These liquors can originate, for example, in the case of adyehouse, from the customary dyeing apparatuses, such as are used fordyeing loose fibre material, tops, yarn and woven fabrics or knittedfabrics, and also from cleaning apparatuses, for example from anopen-width washing machine.

The effluents to be purified are preferably brought into contact in theundiluted state with cellulose material pretreated with precipitants. Inprinciple, three processes are suitable for this purpose:

a. The so-called stirring process, wherein the water to be purified isstirred with the pretreated cellulose material in a vessel and thecellulose material and water are then separated from one another.

b. The so-called flow bed process in which the pretreated cellulosematerial is kept in the suspended state by the counter-current flow ofthe liquor to be purified.

c. The so-called filtration process wherein the liquor to be purified ispassed through pre-treated cellulose filter material.

Of these three process variants, the filtration process (c) ispreferably used, and above all the following three apparatus variantsare suitable.

1. The treatment apparatus, for example dyeing device, is firmlyconnected to the filter apparatus.

2. The filter apparatus is movable and can be coupled to any treatmentapparatus, as required.

3. The effluents originating from the treatment liquors are combined ina suitable vessel and are thereafter filtered conjointly.

The purification of the effluents is preferably carried out at 10° to150° C. However, it is preferably carried out just below the treatmenttemperature, that is to say at between 30° and 130° C depending on thetreatment conditions. The purification of the effluents can also takeplace under pressure, if appropriate.

The cellulose to be used as the carrier material in the purificationconsists, for example, of bleached or unbleached spruce sulphitecellulose, Kraft cellulose or waste sheets from printing, which are in asuitable form. The waste sheets from printing are disintegrated onmachines suitable for this purpose, for example on a Hydrapulper. Thecellulose can be in the form of granules, filter paper or paper pulp.

Suitable precipitants are in principle compounds which are adsorptivelybound by the cellulose and which at the same time exert a precipitatingor retaining action on the residual substances in question such as, forexample, dyestuffs, optical brighteners, washing agents or tanningagents. In this respect, water-soluble basic aminoplasts such asformaldehyde-dicyandiamide condensation products have proved suitable.Advantageous results are conveniently achieved with condensationproducts of formaldehyde, dicyandiamide and urea or an alkylenepolyaminewith 2 to 12, preferably with 2 to 8, carbon atoms, and 2 to 5 aminogroups. The alkylenepolyamines are, for example, tetraethylenepentamine,triethylenetetramine, tributylenetetramine, diethylenetriamine,hexamethylenediamine, ethylenediamine, propylenediamine orbutylenediamine.

Suitable basic aminoplasts are, above all,formaldehyde-dicyandiamide-ethylenediamine orformaldehyde-urea-dicyandiamide condensation products. Preferredproducts are obtained, for example, by condensation of 2 mols offormaldehyde with 1 mol of the reaction product of 2 mols ofdicyandiamide with 1 mol of ethylenediamine, or the corresponding acidsalt such as the hydrochloride. Other products which are also preferredare manufactured by condensation of 1 mol each of urea, dicyandiamideand formaldehyde in the presence of acid such as hydrochloric acid.

Further products are obtained by condensation of 3 to 4 mols ofdicyandiamide with 7 mols of formaldehyde and 1 mol of thetetrahydrochloride of triethylenetetramine.

However, precipitants of particular practical interest are thepolyamidopolyamines which are obtained by reaction of polymerised,preferably dimerised to trimerised, fatty acids with polyamines,preferably in such a ratio that the resulting polyamide resin has anamine value in the range of about 200 to 650 mg of potassium hydroxideper gram of polyamide. As polyamines which can be used for themanufacture of polyamides it is possible to employ aromatic polyaminesor especially aliphatic polyamines which can also contain heterocyclicstructures, such as imidazolines. Polymeric fatty acids, which areadvantageously present in such polyamides, are obtained bypolymerisation of one or more unsaturated long-chain aliphatic oraromatic-aliphatic acids or their esters or other derivatives which caneasily be converted into the acid. Suitable examples of such polymericfatty acids are described in British patent specification Nos. 879,985and 841,554.

These polyaminoamides can be employed by themselves or in combinationwith the abovementioned dicyandiamide condensation products.

The polymeric unsaturated fatty acids used here are advantageouslyaliphatic ethylenically unsaturated dimeric to trimeric fatty acids.Preferably, the polyamides from polyalkylenepolyamines and aliphaticethylenically unsaturated dimeric to trimeric fatty acids, which arederived from monocarboxylic acids with 16 to 22 carbon atoms, aremanufactured. These monocarboxylic acids are fatty acids, with at leastone and preferably 2 to 5 ethylenically unsaturated bonds.Representatives of this class of acids are, for example, oleic acid,hiragonic acid, elaeostearic acid, licanic acid, arachidonic acid,clupanodonic acid and especially linoleic acid and linolenic acid. Thesefatty acids can be obtained from natural oils wherein they occur, aboveall, as glycerides.

The dimeric to trimeric fatty acids are obtained in a known manner bydimerisation of monocarboxylic acids of the indicated type. Theso-called dimeric fatty acids always contain trimeric acids and a smallamount of monomeric acids.

Dimerised to trimerised linoleic or linolenic acids are particularlysuitable. The technical products of these acids as a rule contain 75 to95 percent by weight of dimeric acid, 4 to 22 percent by weight oftrimeric acid and 1 to 3% of monomeric acid. Accordingly, the molarratio of dimeric to trimeric acid is about 5:1 to 36:1. Polymeric fattyacids or esters which are used for the manufacture of the reactivepolyamides can also be epoxidised, for example by reaction withperacetic acid, performic acid or hydrogen peroxide and formic acid oracetic acid. Suitable epoxidised fatty acids and esters are described inBritish patent specification Nos. 810,348 and 811,797.

Polyamides which can be used according to the invention can also becondensation products of polymeric fatty acids with polyamines, asdescribed in British patent specification Nos. 726,570 and No. 847,028,it being possible to react these products with epoxide resins which areproduced by reaction of polyhydric phenols with polyfunctionalhalogenohydrins and/or glycerinedichlorhydrin and which are described inU.S. Pat. Nos. 2,585,115 and 2,589,245.

Reactive forms of polyamides obtained by condensation polymerisation, athigh temperatures, from a reaction mixture which contains polymericfatty acids (manufactured according to British patent specification Nos.878,985 and No. 841,544), monomeric fatty acids and lowpolyalkylenepolyamines can also be used in the present invention.

Suitable polyamide resins which can be used for the manufacture of thefilter materials which can be employed according to the invention aredescribed, for example, in British patent specification Nos. 726,570,810,348, 811,797, 847,028, 865,656 and 1,108,558, for example thecompounds which are sold under the tradenames "Versamid 115", "Versamid125", "Versamide 140", "Ancamid 400", "Beckalide K 189", "Casamid 167","Casamid 185M", "Genamid 2000", "Genamid 250", "Synolide 960","Merginamide L 410" and "Wolfamid No. 4" ("Ancamide", "Beckalide","Casamid", "Genamid", "Synolide", "Merginamide", "Versamid" and"Wolfamid" are trademarks).

Further precipitants are the polymers of an alkyleneimine with 2 to 4carbon atoms which have a molecular weight (MW) of 20,000 to 80,000,preferably 30,000 to 40,000. Suitable alkyleneimines are in particularethyleneimine, propyleneimine, 1,2-butyleneimine and 2,3-butyleneimine.Of all the alkyleneimines, ethyleneimine is preferentially used.

Precipitants which consist of two components are also suitable for themanufacture of filter material of particularly high performance. Suchprecipitants are manufactured in a simple manner by polymerprecipitation in the presence or absence of cellulose. This polymerprecipitation is preferably carried out by precipitating theabovementioned polymeric poly-cationic precipitants in an aqueous mediumby means of a poly-anionic polymer. In this way, sparingly water-solublepolymer associates are produced, which are absorbed on the surface ofthe cellulose which may have been present during the precipitation. Ifthe polymer precipitation is carried out in the absence of cellulose,the resulting polymer associates are subsequently applied, in a suitableform, to the cellulose.

Optionally substituted homopolymers or copolymers of aliphaticα,β-ethylenically unsaturated carboxylic acids, advantageously in theform of their alkali metal salts, especially of the sodium or potassiumsalts, or in the form of their ammonium salts, optionally mixed withcorresponding free polycarboxylic acids, have above all proved suitableas poly-anionic polymeric precipitants.

Preferably, water-soluble optionally substituted homopolymeric acrylicacids are used, for example homopolymers of the following monomers:acrylic acid, methacrylic acid, α-ethylacrylic acid, α-isopropylacrylicacid, α-butylacrylic acid and α-chloroacrylic acid. Water-solublehomopolymers of acrylic or methacrylic acid with a molecular weight of20,000 to 1,000,000, especially with a molecular weight of 50,000 to150,000, are particularly preferred.

Copolymeric aliphatic α,β-ethylenically unsaturated carboxylic acids areabove all copolymerisation products of acrylic acid and methacrylicacid, but also copolymerisation products of acrylic acid or methacrylicacid with another substituted acrylic acid mentioned earlier.

Further poly-anionic copolymerisation products are obtained bycopolymerisation of acrylic or methacrylic acid with compoundscontaining vinyl groups and capable of copolymerisation, especially withwater-soluble or water-insoluble comonomers. As examples ofwater-soluble comonomers there may be mentioned:

a. comonomers containing sulphonic acid groups, such as styrenesulphonicacid;

b. comonomers containing carboxylic acid groups, such as crotonic acid;

c. comonomers containing carboxylic acid amide groups, and theirN-hydroxyalkyl derivatives, such as acrylic acid amide, methacrylic acidamide, N-hydroxymethyl-, N-β-hydroxyethyl-, N-γ-hydroxypropyl- andN,N-bis-β-hydroxyethyl-acrylic acid amide, and N-hydroxymethyl-,N-β-hydroxyethyl-, N-γ-hydroxypropyl- andN,N-bis-β-hydroxyethyl-methacrylic acid amide;

d. water-soluble, especially sulphonated, derivatives ofβ-hydroxyalkyl-acrylic acid amides or -methacrylic acid amides which areobtained, for example, by condensation of acrylic acid halides ormethacrylic acid halides, especially chlorides, with reaction productsof alkanolamines and chlorosulphonic acid;

e. copolymerisable aldehydes, such as acrolein or crotonaldehyde.

As examples of suitable water-insoluble comonomers there may bementioned:

i. acrylic acid alkyl esters or methacrylic acid alkyl esters with 1 to12 carbon atoms in the alkyl radical, which can optionally besubstituted further, especially by hydroxyl groups, such as acrylic acidor methacrylic acid methyl esters, ethyl esters, β-hydroxyethyl esters,n-butyl esters and dodecyl esters;

ii. vinyl esters of aliphatic carboxylic acids possessing 1 to 12 carbonatoms or of mixtures of such carboxylic acids suc as vinyl acetate,vinyl formate, vinyl butyrate or vinyl esters of the carboxylic acidmixture with 9 to 11 carbon atoms known under the tradename VEOVA 911(also called "Versatic Acid" vinyl ester).

iii. Vinyl benzenes, such as styrene, chlorostyrene and methylstyrene.

The poly-anionic polymers mentioned can be manufactured in a mannerwhich is in itself known, in aqueous solution or suspension, under theaction of catalysts, preferably radical-forming catalysts, such ashydrogen peroxide, ammonium persulphate, potassium persulphate ororganic peroxides, for example dibenzoyl peroxide, or by using ammoniumpersulphate and sodium bisulphite. They are appropriately manufacturedat a temperature between 40° and 100° C.

Carboxymethylated cellulose derivatives can be employed as furtherpoly-anionic precipitants. Carboxymethylcellulose, which as a rule isused in the form of its water-soluble alkali metal salts, such as thesodium salt or potassium salt, is particularly suitable. Suchcarboxymethylcellulose derivatives appropriately have a degree ofsubstitution (DS) of 0.4 to 2; carboxymethylcellulose salts with DS =0.7 to 1.2 are preferred. (The degree of substitution DS is definedaccording to Enc. of Polym. Sci. and Technol. volume 3, page 468). Theamount of anionic precipitant employed advantageously fluctuates between10 and 200%, relative to the cationic precipitant. Preferably, 20 to100% of the poly-anionic agent are employed.

To manufacture filter material of particularly high performance which inaddition to high retention, for example for anionic dyestuffs andoptical brighteners, also displays a very high retention capacity foranionic surface-active agent and tanning-agents, a combination of theabovementioned precipitants with salts of polyvalent metals such as, forexample, aluminium sulphate, aluminium chloride, iron sulphate, ironchloride, magnesium sulphate, magnesium chloride and calcium chloridehas proved appropriate. Preferably, these metal salts are employed inthe hydrated form of the corresponding neutral or basic metal oxides.This is appropriately done by adding inorganic or organic bases to theaqueous solution of the abovementioned metal salts. As inorganic bases,alkali metal hydroxides are preferably employed, for example sodiumhydroxide, potassium hydroxide and aqueous ammonia, whilst as organicbases alkylamines are above all employed, such as, for example,methylamine, dimethylamine or trimethylamine, ethylamine, diethylamineor triethylamine and alkanolamines such as monoethanolamine,diethanolamine or triethanolamine.

The amount of the metal salts employed advantageously varies between 10and 300% relative to the amount of the precipitant employed. Preferably,50 to 200% of the metal salt are used, relative to the used amount ofthe precipitant employed.

The pretreatment of the cellulosic material with precipitants isappropriately carried out in aqueous suspension, for example at roomtemperature, at 20° C. However, it can also be carried out at anelevated temperature, up to 100° C. The amount of precipitant employedadvantageously varies between 0.5 and 20% relative to the cellulosicmaterial. Appropriately, 2-10% are employed for this purpose.

As preparation for the pretreatment, the cellulose or waste sheets fromprinting are converted into a form suitable for this purpose, especiallyinto a fibre suspension. Depending on the temperature conditions chosen,the duration of the pretreatment can vary between a few minutes andseveral hours. The pretreated cellulose is subsequently converted intofilters or filter materials according to known methods.

Dyestuffs which are removed from the effluents by the process accordingto the invention can be both water-soluble and water-dispersibledyestuffs or optical brighteners. The process is preferentially suitablefor the removal of water-soluble, especially anionic, dyestuffs oroptical brighteners.

In the case of water-soluble dyestuffs, dyestuffs which are retainedparticularly well are those which are water-soluble because of thepresence of acid groups, such as carboxylic acid groups, but especiallysulphonic acid groups or acid sulphuric acid ester groups. They can bereactive or unreactive towards the fibre material to be dyed and canfurthermore belong to the most diverse categories, such as, for example,those of the styryl, oxazine, formazane, quinophthalone,triphenylmethane, xanthene, perinone, azomethine, nitro, nitroso,acridone or phthalocyanine dyestuffs or especially the metallised,metal-free or metallisable monoazo or polyazo dyestuffs.

The retaining action is very particularly pronounced in the case of theso-called direct dyestuffs. However, the retaining capacity is alsoconsiderable in the case of metal complex dyestuffs.

The process according to the invention is not only suitable for thedecolourisation of residual liquors which arise in the dyeing oftextiles, paper or leather but also performs valuable service when it isa matter of removing residues of optical brighteners from washingliquors and bleaching liquors. Particularly favourable results areobtained in those cases in which the optical brightener to be eliminatedis of anionic character. Examples of such brighteners are:4,4'-bis-(acylamino)-stilbene-2,2'-disulphonic acids,4,4'-bis-(triazinylamino)-stilbene-2,2'-disulphonic acids,4,4'-bis-(azolyl)-stilbene-2,2'-disulphonic acids,stilbylnaphthotriazoles, bis-(benzoxazol-2-yl) derivatives,monomethine-cyanines,2,7-bis-(aroylamino)-dibenzothiophene-dioxide-3,6-disulphonic acids,1,3-diaryl-pyrazolines, styrylbenzoxazoles, bis-styrylaryl compounds,bis-benzoxazolylaryls or oxadiazoles.

A further advantage of the process according to the invention is basedon the fact that it permits elimination of anionic surface-active agentsand anionic dyeing auxiliaries from aqueous waste liquors. Such anioniccompounds are described in more detail in the book"Tenside-Textilhilfsmittel-Waschrohstoffe" ("Detergents-TextileAuxiliaries-Raw Materials for Washing Purposes") by Dr. Kurt Linder(published by Wissenschaftliche Verlagsgesellschaft MBH Stuttgart 1964),volume 1; pages 561-835. Anionic compounds of the alkylarylsulphonicacid type are of particular practical interest. The retaining capacityis very particularly pronounced in the case of anionic compounds of thealkylarylsulphonic acid type, in which the alkyl part has 10 to 14carbon atoms.

The process according to the invention can also be of assistance incases where the elimination of anionic synthetic tanning agents,especially tanning agents which carry one or more sulpho groups in themolecule, is concerned. Such compounds are well-known to experts underthe name "Syntane". A more detailed description of these compounds is tobe found in "Ullmanns Encyklopadie der technischen Chemie" ("UllmannsEncyclopaedia of industrial Chemistry"), volume 11; pages 595-598.

By suitable choice of the precipitant it is possible, according to theinvention, to remove up to 100% of the impurity from the effluents.Retention effects of more than 4 g of residual substance, that is to saydyestuff, optical brightener, auxiliary, washing agent or tanning agent,per 100 g of cellulose filter can thereby be achieved. In cases in whichit does not prove possible to achieve complete decolourisation orremoval of the residual substances by a single pass of the residualliquor through the filter, it is advisable to repeat the filtrationprocess.

It is also possible to reduce the filter materials used to a minimum bythe same measure (recirculation).

A particularly economical advantage of the process according to theinvention is that the pretreated cellulose filters after saturation withthe residual substances from the effluents can be dried in a simplemanner and thereafter be passed to an incinerator. A further advantagemay be considered to be the fact that waste sheets from printing, theuse of which in most cases presents problems, are very suitable for usein the process according to the invention.

The examples which follow explain the invention without restricting itthereto. In the examples, percentages are percentages by weightthroughout.

MANUFACTURING INSTRUCTIONS Precipitant

A. 34 kg of dicyandiamide, 18 kg of urea and 5.5 kg of ammonium chloridein 75 kg of 30% strength hydrochloric acid are boiled for 6 hours underreflux. Thereafter, 80 kg of 37.4 % strength aqueous formaldehydesolution are added and the whole is stirred for 6 hours at 75°-85° C.After completion of the condensation, 10 kg of glacial acetic acid areadded to the solution.

B. A mixture of 533 g of ethylenediamine dihydrochloride and 673 g ofdicyandiamide is introduced in small portions, over the course of about2 hours and whilst stirring, into a flask which is immersed in a heatingbath at 250°-255° C. An easily stirrable melt is thereby produced. Themixture is stirred for a further hour at an internal temperature of250°-255° C. During introduction of the mixture and during subsequentstirring, ammonia is split off. Thereafter the internal temperature islowered to about 155° C, whereupon 147 g of glacial acetic acid areallowed to run in over the course of about 5 minutes. The internaltemperature is lowered to about 115° C by further cooling and 107 g ofparaformaldehyde are introduced over the course of about 15 minutes. Theinternal temperature is then allowed to drop to 100° C and 363 g of 37%strength aqueous formaldehyde solution are added over the course ofabout 5 minutes. The mixture is now heated for about 10-15 minutes in aboiling water bath, in the course of which the reaction mixturethickens, 600 g of water at about 90° C are allowed to run in and thebatch is heated further, for a total of 2 hours, in the boiling waterbath. In the course thereof, a clear solution is produced after about 20minutes. The internal temperature is lowered to about 50° C, the mixtureis neutralised by adding sodium bicarbonate, and the reaction product isdried at 50°-60° C under reduced pressure. An almost colourless, solidresidue is obtained, which gives a clear solution in boiling water.

Filter material

C. A suspension of 10 kg of bleached spruce sulphite cellulose in 300 kgof water is mixed with 2.5 kg of the aqueous solution of dicyandiamide +urea + formaldehyde condensation products according to Instruction A,described above. The entire mass is stirred for 21/2 hours at 30°-40° C.Thereafter the pretreated cellulose is filtered off and dried. The 10 kgof cellulose contain 170 g of the condensation product A bound byabsorption.

D. If the 10 kg of bleached spruce sulphite cellulose in Instruction Care replaced by 10 kg of waste sheets from printing, in the form of afine suspension, and the pretreatment is carried out as described underC, with a product according to Instruction B, a filter material whichhas similarly good properties is obtained.

E. If, in Instruction C, the spruce sulphite cellulose is replaced byKraft cellulose, a filter material which has similar properties isobtained.

F. If, in Instruction C, the 2.5 kg of the precipitant A are replaced by1 kg of Versamid 140, a polyamide having an amine value of 350 to 400 mgof KOH/g, an effective filter material is obtained.

G. If, in instruction C, the precipitant A is replaced by a combinationof 200 g of Versamid 140 with 200 g of FeCl₃.6H₂ O, a filter materialwhich has very good properties is obtained.

H. A suspension of 10 kg of bleached spruce sulphite cellulose in 100 kgof water is mixed with 800 g of 500% strength polyethyleneimine (M.W.30-40,000). The entire mass is kneaded mechanically for 20 minutes. Thismixture is subsequently dried in a vacuum oven at 90° C.

I. A suspension of 10 kg of finely chopped waste sheets from printing in300 kg of water is stirred with 1 kg of Versamid 140 for 3 hours at atemperature of 20°-25° C. After this time, the fine suspension ispressed out to 30 kg. The filter cake is dried in a vacuum oven at80°-90° C. The dry mass is comminuted and stirred into 300 kg of water.5 l of a 10% strength AlCl₃ solution are allowed to run in and after 20minutes 2 l of ammonia solution (25% strength) are added to the aqueoussuspension. The mass is again pressed out to 30 kg and dried in a vacuumoven at 90° C.

J. If, in Instruction H, the polyethyleneimine is replaced by acombination of 800 g of 50% strength polyethyleneimine with 1,025 g ofAl₂ (SO₄)₃.18H₂ O, a further suitable filter is obtained.

K. A suspension of 10 kg of bleached spruce sulphite cellulose in 500 kgof water is treated with 1 kg of Versamid 140. The suspension is stirredfor 300 minutes at 20° C. 33.5 l of a 1% strength polymethacrylic acidsolution (M.W. 80-100,000) which has been adjusted to pH=6.1 with sodiumhydroxide solution are stirred into this suspension over the course of20 minutes. The mass is stirred for an additional short period and 6.67l of a 10% strength AlCl₃ solution are added. Thereafter the pH value ofthis suspension is adjusted to 9.5 with a 10% strength ammonia solution,the whole is stirred for about 60 minutes, and the filter material ispressed out to 30 kg. The filter material is used directly, in thismoist state, for the purification of the effluents.

L. A suspension of 10 kg of bleached spruce sulphite cellulose in 500 kgof water is treated with 1 kg of Versamid 140. The suspension is stirredfor 300 minutes at 20° C. 67.0 l of a 1.5% strength solution of thesodium salt of carboxymethylcellulose (D.S. approx. 0.8) were stirredinto this suspension over the course of 20 minutes. The mass issubsequently stirred for an additional short period and pressed out on afilter to a weight of approx. 30 kg. A readily usable filter material isobtained.

M. The filter is manufactured in the same way as in Instruction L, but 1kg of Versamid 140 is replaced by 1 kg of polyethyleneimine (M.W.30-40,000) and the 67.0 l of a 1.5% strength carboxymethylcellulosesolution are replaced by 67.0 l of a 1% strength polymethacrylic acidsolution (M.W. 80-100,000).

EXAMPLE 1

2,000 l of a residual liquor of dark blue colour, which still contains200 g of the dyestuff of the formula ##STR1## in the dissolved form arepassed, at a temperature of 95°-98° C, through a filter manufacturedaccording to Instruction C. The filtrate resulting under theseconditions is now colourless.

If the same filtration is carried out using 10 kg of untreatedcellulose, only 35% of the total dyestuff are retained.

EXAMPLE 2

400 l of an intensely orange-coloured residual liquor which stillcontain 40 g of the dyestuff of the formula ##STR2## are filteredthrough 1 kg of spruce sulphite cellulose pretreated according toInstruction C. The filtrate obtained under these conditions ispractically colourless.

A similarly good result is obtained if instead of the pretreated sprucesulphite cellulose according to Instruction C the same amount of Kraftcellulose, according to Instruction E, treated in the same manner isemployed.

EXAMPLE 3

2,000 l of a blue-coloured residual liquor which still contains 100 g ofdissolved dyestuff of the formula ##STR3## are filtered through 10 kg ofcellulose treated according to Instruction C, at a temperature of90°-95° C. If these conditions are observed, 80% of the dyestuff areretained. If this filtrate, containing 20% of the residual dyestuff, isfiltered a second time through the filter material which has alreadybeen used, a completely decolourised filtrate is obtained. If the samefiltration is carried out using cellulose which has not been pretreated,the dyestuff retention is only 7%.

EXAMPLE 4

1,000 l of a brown-coloured residual liquor which still contains 50 g ofdyestuff of the formula ##STR4## are passed, at a temperature of 85° C,through a filter consisting of 5 kg of cellulose pretreated according toInstruction C. The resulting filtrate proves to be largely colourless.

If the cellulose pretreated according to Instruction C is replaced bythe same amount of waste sheets from printing, pretreated according toinstruction D, a largely colourless filtrate is again obtained.

EXAMPLE 5

2,000 l of a residual liquor which still contains 9.2 g of the opticalbrightener of the formula ##STR5## are forced, at a temperature of75°-80° C, through a filter consisting of 10 kg of spruce sulphitecellulose which has beforehand been treated according to Instruction C.The resulting filtrate has been completely freed of the opticalbrightener.

If, in this example, the 10 kg of spruce sulphite cellulose pretreatedaccording to Instruction C are replaced by 10 kg of Kraft cellulosewhich is treated, according to Instruction C, with a condensationproduct manufactured according to Instruction B, a filtrate which hasbeen completely freed of the optical brightener is again obtained.

EXAMPLE 6

1,000 l of a residual liquor which still contains 8 g of an opticalbrightener of the formula ##STR6## are passed, at a temperature of35°-40° C, through a filter consisting of 5 kg of cellulose pretreatedaccording to Instruction C. The filtrate obtainable in this manner hasbeen completely freed of the abovementioned optical brightener.

EXAMPLE 7

2,500 l of a residual liquor of dark red colour, which has been adjustedto pH 4 and contains 250 g of the dyestuff of the formula ##STR7## inthe dissolved form, are passed, at a temperature of 95°-98°, through afilter manufactured according to Instruction F.

The filtrate resulting under these conditions is low colourless.

EXAMPLE 8

3,400 l of a residual liquor of dark red colour, which has been adjustedto pH 4 and contains 340 g of the dyestuff of the formula ##STR8## inthe dissolved form, are passed, at a temperature of 95°-98° C, through afilter manufactured according to Instruction G. The filtrate resultingunder these conditions is practically colourless.

If the same filtration is carried out using filter material described inExample 7, only 2,000 l of the dyestuff solution can be decolourised.

EXAMPLE 9

2,000 l of a residual liquor of dark red colour, which has been adjustedto pH 4 and which contains 200 g of the dyestuff mentioned in Example 7,in the dissolved form, are passed at a temperature of 95°-98° C througha filter manufactured according to Instruction H. The filtrate resultingunder these conditions is completely colourless.

EXAMPLE 10

4,600 l of a residual liquor of dark red colour which has been adjustedto pH 4 and which still contains 460 g of the dyestuff described inExample 7, in the dissolved form, are passed at a temperature of 95°-98°C through a filter manufactured according to Instruction J.

The filtrate resulting under these conditions is colourless.

EXAMPLE 11

9,000 l of a residual liquor of dark red colour, which has been adjustedto pH 4 and which contains 900 g of the dyestuff mentioned in Example 7,in the dissolved form, are passed at a temperature of 95°-98° C througha filter manufactured according to Instruction K. The filtrate resultingunder these conditions is practically colourless.

EXAMPLE 12

6,000 l of a residual liquor of dark red colour, which has been adjustedto pH 4 and which contains 600 g of the dyestuff mentioned in Example 7,in the dissolved form, are passed at a temperature of 95°-98° C througha filter manufactured according to Instruction L. The filtrate resultingunder these conditions is practically colourless.

EXAMPLE 13

7,500 l of a residual liquor of dark red colour, which has been adjustedto pH 4 and which still contains 750 g of the dyestuff mentioned inExample 7, in the dissolved form, are passed at a temperature of 95°-98°C through a filter manufactured according to Instruction M. The filtrateresulting under these conditions is practically colourless.

EXAMPLE 14

8,500 l of a rinsing liquor of dark red colour, which has been adjustedto pH 4 with acetic acid and which contains 850 g of the dyestuffdescribed in Example 7, and 1,940 g of an anionic auxiliary of theformula ##STR9## in the dissolved form are passed, at a temperature of95°-98° C, through a filter manufactured according to Instruction K. Theresulting filtrate is completely colourless.

EXAMPLE 15

3,700 l of a dyeing liquor of dark blue colour which has been adjustedto ph 4 and which contains 370 g of the dyestuff of the formula##STR10## and 1,850 g of a dyeing auxiliary of the composition ##STR11##in the dissolved form were passed through a filter manufacturedaccording to instruction I, at a temperature of 95°-98° C. The resultingfiltrate is colourless.

EXAMPLE 16

1,500 l of a washing liquor which has been adjusted to pH 4 with aceticacid and which contains 1,500 g of a detergent of the formula ##STR12##of commercial quality are passed through a filter manufactured accordingto Instruction K, at a temperature of 90°-95° C. The resulting filtrateis practically free of detergent. To test for the detergent, a 100 mlsample of the filtrate was adjusted to pH 4.5 with acetate buffer and 5ml of a 3% strength Al₂ (SO₄)₃.18H₂ O solution were added at roomtemperature. If the detergent is present, a turbidity or precipitateresults. The filtrate resulting from the experiment gave no precipitatewith aliminium sulphate.

We claim:
 1. A process for purifying industrial effluents containingresidual substances comprising dyestuffs, optical brighteners, dyeingauxiliaries, detergents, tanning agents or mixtures thereof, whichcomprises bringing said effluents into contact with a cellulosicabsorbent pretreated with(a) a water soluble basic aminoplast, and (b) apolyanionic polymer.
 2. A process according to claim 1, wherein thewater-soluble basic aminoplast is a condensation product offormaldehyde, dicyandiamide and urea, or of formaldehyde, dicyandiamideand an alkylenepolyamine with 2 to 12 carbon atoms and 2 to 5 aminogroups.
 3. A process according to claim 2, wherein the poly-anionicpolymer is a homopolymer or copolymer of an aliphatic, α,β-ethylenicallyunsaturated carboxylic acid.
 4. A process according to claim 3, whereinthe water-soluble basic aminoplast is aformaldehyde-dicyandiamideethylenediamine condensation product.
 5. Aprocess according to claim 4, wherein the polyanionic polymer is awater-soluble homopolymer of acrylic or methacrylic acid with amolecular weight of 20,000 to 1,000,000.
 6. A process according to claim1, wherein the cellulosic absorbent is pretreated with a mixture of saidbasic aminoplast and polyanionic polymer and a salt of a polyvalentmetal.
 7. A process according to claim 6, wherein the cellulosicabsorbent is pretreated with a mixture of said basic aminoplast,polyanionic polymer and salt of a polyvalent metal in the presence of aninorganic or organic base.
 8. A process according to claim 1, whereinthe purification is carried out at 10° to 150° C.